Transcranial magnetic stimulation of the motor cortex correlates with objective clinical measures in patients with cervical spondylotic myelopathy.

STUDY
DESIGN: Prospective cohort study.
OBJECTIVE: To assess the correlation between central motor conduction time (CMCT) and various subjective and objective clinical assessment measures in patients undergoing decompressive surgery for cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: CSM can cause a spectrum of neurological deficits among individuals. Subjective clinical assessments of disease severity may lack the sensitivity of objective tests. Transcranial magnetic stimulation provides objective electrophysiological data on the integrity of the corticospinal tracts, which may be useful for monitoring disease progression or neurological improvement after surgery.
METHODS: Patients undergoing surgical decompression for CSM underwent subjective and objective testing before surgery and at 1, 3, 6, and 12 months after surgery. Subjective measures included modified Japanese Orthopaedic Association score, Neck Disability Index, Nurick grade, and visual analogue scale score. Objective measures included CMCT as measured using transcranial magnetic stimulation, the 10-m walk test, the 9-hole peg task, and the grip and release test. Primary outcome was the correlation between CMCT and subjective or objective measures at preoperative and postoperative time points. Secondary outcome was the correlation between preoperative CMCT and performance in subjective or objective testing after surgical intervention.
RESULTS: Improvement in both subjective and objective measures was observed after surgery. CMCT correlated with other objective measures (10-m walk test, 9-hole peg task, and grip and release test) both at baseline and after decompressive surgery in these 17 patients with CSM. Patients with high baseline CMCTs were associated with poor performance on the 10-m walk test, 9-hole peg task, and grip and release test. Modified Japanese Orthopaedic Association score correlated with CMCT at baseline but not after surgical intervention. CMCT was not associated with other subjective measures, such as Neck Disability Index, Nurick grade, and visual analogue scale score, at preoperative or postoperative time points.
CONCLUSION: CMCT as measured by transcranial magnetic stimulation is a responsive objective assessment of CSM. It can be used to monitor disease severity and neurological function before and after surgical intervention. Prolonged baseline CMCT may be associated with worse surgical outcomes. LEVEL OF EVIDENCE: 2.